Electric heater



May L20, 1941. G. sTElNGRUBER ELECTRIC HEATER Filed Feb. 9, 1940 2 Sheets-Sheet 1 May 20, 1941. G. STEINGRUBER ELECTRIC HEATER Filed Feb. 9, 1940 2 Sheets-Sheet 2 Patented May 20, 1941 UNITED sTATEs PATENT OFFICE ELECTRIC HEATER George Stelllgruber. Shelbyville, Tenn.

Avplltion February 9, 194|, Serial No. 318,159

(Cl. 21S-38) Claima.

This invention relates to electric heaters. and more particularly to an improved electric heater which is primarily adapted for use in association with hot-air heating plants or systems.

At the present time, two main types of hot-air heating systems are employed in the heating of dwellings and similar buildings. Each oi' these systems embodies a furnace in which a fuel is burned to heat the air in an air chamber which forms a part of the furnace. According to one type of these systems, the heated air is carried from the air chamber through one or more ducts or pipes to the room or rooms to be heated, where it is discharged into the room through an outlet provided in the floor or wall, and commonly termed a register. In the other type of system. the heated air is taken directly from the furnace and discharged through an outlet provided in the floor immediately above the furnace, without the intermediary pipes or ducts, such a furnace being known asa pipeless furnace. In either case, a strong circulation of air is normally present in the heating system or plant, and is availed of to carry the heat to the desired point or points to be heated.

It is a well recognized fact that at certain times during the course ou' a year. especially in the spring and fall seasons. the weather is hardly severe enough to require the continued operation of the regular heating system, yet it is sufficiently cold to make it desirable to have the heating system in operation from time to time, or at least part of the time. Such operation, however, is very inenfcient and uneconomical, but is resorted to as a general rule for the sake of comfort.

The present invention ins been developed -as a simple, convenient, and emcient means of producing heat in the hot air system of either of the aforementioned types, without the necessity of starting up the regular furmce, or heating plant, but at the same time availing of the air circulation which is inherent in such a system. to distribute the heat. To this end. my invention essentially comprises a frame having one or more electric heating elements mounted therein, and means for mounting the frame in an air passage or duct of the heating system, preferably adiacent to the outlet or register. As such, the invention may be generally characterized as an electric heater of the insert type.

'Through the provision of specially constructed, quickly-attachable fastening instrumentalities on the frame of my new heater insert or unit, the installation of the heater in either existing or new hot-air systems is simplified to a material extent, and may be conveniently accomplished without any special skill and without the aid of special tools. The fastening instrumentaiitles Just referred to preferably have the form of easily bendable straps or hangers which may be passed through the openings in the grill or grid which usually covers the outlet of each air duct where it terminates at the floor or wall of the room, the straps being then bent around the bars of the grill or grid to support the frame and electric heating elements in a position generally transverse to the direction of iiow of the air through the air duct or passage with which the heater unit is associated. n p

It will be understood. of course, that the num- -ber of electric heater units installed for any given system will depend upon the capacity of the system, the number of registers or hot-air outlets available, and/or the number of rooms which are to be heated. In any case, the electric heaters may be operated independently of the furnace, or they may be used as an auxiliary source of heat to supplement the heat normally produced by the furnace. When operated alone, the electric heater units aord an emcient source of clean, healthful heat without the depletion of oxygen in the air and the discomforting effects usually attending tho forms of heating systems employing combustible fuel.

By reason of the simplicity of my new electric heater construction and the consequent low cost of production thereof, as well as the high eiliclency and economy of operation, it is entirely practicable in many cases to substitute my electric heaters for the usual cumbersome and expensive furnaces ordinarily used to produce heat in a hot-air heating system. Such substitution is considerably less expensive than the replacement of a worn out furnace. Where such a system is converted by the substitution of electric heaters for the combustion furnace, the electric heating elements should be chosen to give the required amount of heat, as by varying the number of electric heating elements and/or their size to suit the conditions of the particular installation. If desired, the electric heaters may -be equipped with selective controls by means of which the number of electric heating elements in operation may be changed at will. This ls particularly advantageous in localitieswhere the atmospheric temperature iiuctuates widely.

Still another important object of my invention is the provision of heat reflecting means in association with the electric heating elements of my newl heater to prevent or minimize the loss of heat through absorption and conduction by the ducts or pipes of the heating system in which the electric heater units are adapted to be mounted. these ducts or pipes being usually constructed of sheet metal. The reflecting means just referred to are preferably adjustable to compensate for reasonable variations in the shape and size of the air ducts or passages in which the heater units are disposed.

Other objects and advantages of the invention will be hereinafter described and the novel features thereof defined by the appended claims.

In the drawings:

Figure 1 is a perspective View oi' an electric heater constructed in accordance with my invention;

Figure 2 is a cross sectional View taken through the heater about on the plane of the line 2-2 of Figure l, and showing the heater in the position which it occupies when mounted in a duct and supported by a grill or grid disposed across the outlet of the duct, the duct and grill or grid being shown in broken lines;

Figure 3 is a view generally similar to Figure 2, with the duct and grill or grid shown in section, and the electric heater unit shown in elevation Figure 4 is a somewhat diagrammatic view oi' a modified type of hot-air heating system commonly known as a pipeless furnace, and showing the manner in which my electric heater unit is used in such a system;

Figure -5 is a top plan view of the outlet of the hot-air heatingv system shown in Figure 4, with the electric heater unit shown in dotted lines beneath the grill or grid. This view also diagrammatically shows the electric circuit for the electric heating unit, and a typical selective control therefor;

Figure 6 is an enlarged vertical sectional view taken through the upper part of the pipeless furnace shown in Figure 4, and also through the electric heating unit which is suspended from the grill or grid over the floor outlet;

Figure 7 is a'horizontal sectional View taken through the upper part of the pipeless furnace shown in Figure 4 on a plane above the electric heater unit, the electric heater unit being shown in top plan, and

Figure 8 is a perspective view of an electric heater unit having a construction which is particularly applicable to pipeless furnaces as shown in Figure 4. n

Like reference characters designate corresponding parts in the several figures of the drawings.

Referring first to Figures 1 to 3 inclusive, I designates a hot-air duct or pipe of a conventional hot-air heating system. Usually, such a system will include a plurality of such ducts or pipes leading from the furnace (not shown) to the room or rooms where the heat is to be discharged through a register in the floor or wall. In Figures 2 and 3, I have shown the floor type of outlet, but it is to be understood that the invention is not limited thereto, since my new electric heater may be also applied to the wall type of outlet which is much the same as the floor type. In the usual system, the duct I terminates in an enlarged outlet box 2 which is recessed below the fl'oor or in the wall, as the case may be. The ducts I and outlet boxes 2 are usually made of sheet metal, and the discharge end of the box 2 is usually covered by a grill or grid 3, having a plurality of apertures 4 therein and forming bars 5, which are preferably availed of to support the electric heating unit which is best illustrated in Figure 1.

The electric heating unit includes a frame generally designated l. The frame l is preferably rectangular in shape and relatively shallow in depth. As clearly shown in Figures l and 2, the sides of the frame 8 are U-shaped or channelshaped in cross section, with the flanges 6', 6 of the channel projecting laterally outwardly from the central axis of the frame. These flanges 8', 3 serve to reinforce or stiften the frame, and while the frame 6 may be made from a continuous length of sheet metal or channel bar stock, I prefer to make each side ofthe frame separately and overlap the adjoining ends of the frame sides, as at 6 to reinforce the corners of the frame. The overlapped sides of the frame may be connected together in any suitable manner, preferably by spot welding.

Disposed Within the frame B and extending transversely thereacross between opposite sides thereof is one or more electric heating elements "I, two such elements being shown in Figures 1 and 2. The heating elements may be of conventional construction, and preferably include a refractory tube 8 about which is wound a resistance wire 9. Each heating element I is preferably yieldably mounted in the frame 6 to minimize breakage or damage of the tube 8 in handling or shipping the heater units. To this end, the opposite sides of the frame 6 are provided at their respective inner sides with a resilient pressure or clamping plate I0, one for the end of each of the heating elements 1. Each plate I0 is rigidly attached to the side of the frame 6, as by spot weldingone end of the same thereto as at II, and the remaining portion of each plate is laterally oiset inwardly of the frame 6 so as to be normally free to move towards and away from the frame. Each plate III is provided with an inwardly-projecting boss or lug I2 which is adapted to be received in one end of the rigid refractory tube 8 which supports the resistance wire 9, and the free extremity of each plate is provided with a laterally outwardly offset ear or tongue I3, which is adapted to bear against the same side of the frame 6 to which the plate III is attached at its opposite end. By arranging the resilient plates III in opposed pairs, one pair for each of the heating elements l, the heating elements may be easily and quickly mounted in the frame C in an obvious manner, after which the ears or tongues I3 on the respective plates I0 are bent`into engagement with the frame 8 to prevent accidental displacement of the heating elements, while at the same time maintaining a yieldable connection between the heating elements and the frame as afforded by the portions of the plates Il which are spaced from the sides of the frame.

According to the arrangement shown in Figures 1 to 3 of the drawings, the corresponding ends of the heating elements 1, 'I are connected together, as by joining the resistance wires 9, at Il. At the opposite ends of the respective heating elements l, 1, the resistance wires are connected, at I5 and I6 respectively, to conductors II and Il, which, in turn, are adapted to be connected to any convenient source of electrical power. The conductors I1, Il are preferably extended through insulated bushings Il and 20 mounted in the side of the frame 6 adjacent to the respective ends of the heating elements II, 1. Such an arrangement minimizes the possibility of short-circuiting the heating elements or otherwise grounding the electrical circuit on the frame. In the arrangement just described, the heating elements l, 1 will be in series, suitable for a 220-volt A. C.

or D. C. circuit, but it is to be understood that the invention is not limited to a series arrangement oi' the heating elements, since the heating elements may be connected across the feed wires in paralleLif preferred. y

Secured to the frame 8, preferably adjacent to each corner thereof, is a hanger or strap 2| by means of which the heater unit may be quickly attached to a support. such as the grill or grid 3 which is usually provided across each outlet of the hot-air heating system. These hangers or straps 2| are preferably made of easily bendable sheet metal or other form-retaining material capable of supporting the weight of the heating unit. As shown, the hangers 2| are secured to the frame I by spot welding, although they may be attached in any other convenient manner, and the straps or hangers are made long enough so that they may be passed through the openings l in the grill or grid 3 and bent around the bars I thereof, as clearly shown in Figures 2 and 3. In this manner, the heater unit is suspended from the grill or grid, and it will be understood that no special skill or special tools are required to attach the heater unit in an operative position behind the grill or grid. After mounting the heater unit in position behind the grill or grid and within the outlet box 2 at the discharge end of the air duct or pipe I, it is simply necessary to connect the conductors |1, I8 to the current supply line, which may be done by tapping into the electrical wiring system of the building in which the heating plant is located, or by running an extension cord from the heating elements 1, 1 to any standard electrical outlet which may be conveniently accessible.

In order to minimize loss of heat by absorption and conduction of the heat by the sheet metal outlet box 2 and ducts I preferably attach to each side of the frame 8 of the heater unit a reflector plate which is extended substantially beyond the frame at one side thereof. In the case of an installation of the heater unit in the outlet box below the floor, the reflector plates depend below the frame 8, as clearly shown in Figures 2 and 3, with the lower extremities of the reflector plates disposed contiguous to the walls of the outlet box 2. 'I'he reflector plates are generally designated 22 and are arranged in opposed pairs 22', 22', and 22", 22". The retlector plates 22', 22' are preferably connected at their upper ends to the lower flanges of the respective sides of the frame 6 which carry the resilient supporting plates I which support the heating elements 1. This connection may be conveniently made by providing the plates 22', 22 with laterally outwardly projecting flanges 23, and spot welding these flanges to the lower flanges of the frame 6. Since these reflector plates 22', 22 are disposed at the ends of the heating elements 1, it is not necessary to extend the same within the frame 8 where the intensity of the heat is not as great at the ends of the heating elements 1 as it is below and along the longitudinal sides of the heating elements. However, the other pair of reflector plates 22", 22" are preferably extended through the frame 8 and are respectively provided with a laterally outwardly bent flange 23' for attachment to the upper flange of the frame 6. The corners of the flanges 23', 23 of the reflector plates 22", 22" are cut away, as at 24, to clear the hangers or straps 2|. The flanges 23' are preferably spot welded to the flanges of the frame 8 on which they overlap, and, if desired, the reflector plates 22", 22" may each be spot welded to the inside of the frame l. For a more complete lunderstanding of the spot welded assembly, it will be noted that the` spot welds are represented by broken circles.

'I'he reflector plates generally designated 22 are preferably composed of sheet metal having a highly polished reflecting surface, or the sheet metal plates may be chromium-plated or otherwise coated to produce the reflecting characteristic desired. The reflecting plates are sumciently flexible to enable the same to be readily bent inwardLv or outwardly respecting the central axis of the heater unit to allow for reasonable variation in the positioning of the heater unit within`V the outlet box 2 of the heating system. As shown in Figures 2 and 3, the outlet box 2 tapers downwardly and inwardly, and the reector plates 2'2 are also preferably tapered at their opposite ends so that they may normally be adjusted to converge in a downward direction. The extent of this convergence will depend upon the taper of the outlet box 2 whlchmay vary in different heating systems. In installing the electric heaters, it is desirable to dispose the same in the outlet box 2 so that the heating elements 1 are spaced several inches from the grill or grid l3, which extends across the discharge end of the outlet box. While this spacing is not critical, it will necessarily vary Ibecause of the usual variations in the depth of the outlet box, for which reason the hangers or straps 2| are made of substantial length.

Passing now to the modified construction illustrated in Figures 4 to 8 inclusive, 25 generally designates in a more or less diagrammatic form a conventional pipeless furnace. Such a construction is usually provided with a central combustion chamber 26 disposed within a central air heating chamber 21. The chamber 21 is jacketed to provide a fresh or cold air passage 28, which communicates at its lower end with the lower end of the chamber 21. The air intake passage 28 and the heating chamber 21 both extend directly upwardly to the floor above the furnace in which there is provided a large outlet covered by a grill or grid 28. The cold or cool air passes downwardly through the grill or grid 29 at the margins of the latter and thence downwardly through the passage 28 of the furnace and into the lower end of the heating chamber 21. As the air rises in the chamber 21, it is heated by the combustion of the fuel in the combustion chamber 28, and then passes upwardly where it is ultimately discharged through the central part of the grill or grid 28. Such a system may likewise be equipped with my electric heater, as generally indicated at 38. The heater unit 30 is similar to that shown in Figures 1 to 3 inclusive excepting that it is of larger capacity, and the reflector plates have been omitted, since they are not necessa in an installation of this type wherein the wal of the air passage are vertical at the outlet of the heating chamber 21 of the furnace 25. In this modified heating unit, 3| designates the frame which is suspended by the hangers 32 in a manner similar to that previously described. The heating elements 33 are mounted in the frame 3| between the resilient plates 34, corresponding to the plates Ill in Figures 1 to 3. I have shown six heating elements 33 in the frame 3|, this number having been found to be adequate for the average installation in the "pipeless furnace" type of heating system, although it is to be understood that the number of heating elements may be more or less, if preferred.

In Figure 5, I have diagrammatically shown a typical electric circuit wherein the heating elements 33 are arranged in two groups of three heating elements per group, and the heating elements of each group are connected in parallel with the heating elements of the other group. A switch 35 is disposed in the electric circuit so that when the switch is in the position shown in Figure 5, all of the heating elements 33 will be con-- nected to the feed wires 33 which supply current to the heater. By actuating the switch 35 (in a downward direction as viewed in Figure 5) one group of the heating elements 33 will be disconnected from the feed wires 36, leaving only half the number of heating elements in the circuit. It will be understood, of course, that by modifying the electric circuit and the control switch, a greater selection of energization and deenergization of the heating elements 33 may be had, as will be obvious to those skilled in the art.

Inlieu of the manually operable switch 35, a thermostatic control of any conventional type may be usedl to automatically disconnect all or certain of the electric heating elements from the supply line when the temperature of the room reaches the desired limit, and to automatically connect the heating elements to the supply line when the temperature of the room falls below the desired limit. A similar automatic control may also be applied to the heater unit shown in Figures 1 to 3.

The' operation of the heater in both of its forms respectively shown in Figures 1 to 3 and 4 to 8 will be apparent from the foregoing description. In both cases, the heat is effectively distributed automatically by the air circulation which is inherent in the heating system, and lrrespective of whether or not the furnace is in operation. The air flowing through the system comes into contact with the heating elements 1 or 33, as the case may be, which are disposed in a position generally normal to the direction of air fiow, and the air entrains the heat and is ultimately discharged through the grill or grid from which the heating elements are supported.

While the specific details of construction have been herein shown anddescribed, the invention is not confined thereto as alterations may be made Without departing from the spirit thereof as defined by the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A heater of the class described, comprising a frame, an electric heating element extending transversely across said frame, and quickly-attachable means carried by the frame comprising a plurality of bendable supports extending from the margin of thel frame in spaced relation to each other adapted to be bent around the bars of a grill or grid.

2. A heater of the class described, comprising a frame of generally rectangular form, at least one electric heating element extending transversely within the frame between opposite sides thereof, and a hanger member connected to said frame adjacent to each corner thereof, each hanger member comprising a readily bendable strap of, form retaining material.

3. A heater of the class described, comprising a frame of generally rectangular form, at least one electric heating element extending transversely within the frame between opposite sides thereof, attaching means carried by thev frame and adapted to be attached to a support, and reflector means carried by each side of the frame and extending to one side of the plane thereof, each of ysaid reflector means being formed of flexible material so as to be adjustable indepcndently of the other reflector means.

4. A heater of the class described, comprising a frame, an electric heating element extending transversely across said frame, and means connected to the frame for securing the same to a grill or grid of an air circulating system, ysaid frame extending about an axis normal to the plane thereof and of relatively shallow depth, the sides of Ythe frame being channel-shaped in cross section and separately constructed with their adjoining ends overlapping each other to reinforce the corners of the frame.

5. A heater of the class described, comprising a relatively shallow frame of generally rectangular form and having its sides disposed about an axis normal to the plane of the frame3 anvelongated relatively rigid electric heating element disposed within the frame and extending between opposite sides thereof, and means mounted on the respective opposite sides of the frame aforesaid for exerting a, yieldable endwise clamping pressure upon the opposite ends of the heating element, said last-named means comprising a flexible plate fixed at one end to the frame and spaced from the frame beyond its fixed end so as to be movable towards and away from the frame, means on the plate intermediate the ends thereof 'for engaging the contiguous end of the heating element, and said plate having a part laterally offset therefrom at its free end towards the side of the frame to which the plate is attached to engage said frame and support the free end of the plate against movement toward the frame.

GEORGE STEINGRUBER. 

